Breeding Biology of the Tawny-Bellied Seedeater (Sporophila hypoxantha) In Southern Brazilian Upland Grasslands

Abstract We present detailed information on the breeding biology of a migratory population of the Tawny-bellied Seedeater (Sporophila hypoxantha), a typical member of the “capuchinos” group. Data were collected for 69 nests from 2007–2010 in areas of hilly dry grasslands in southern Brazil. Breeding begins in early November, a week after the seedeaters arrive, peaks in late November, and lasts until late February, when individuals migrate north. Females build small open-cup nests in small shrubs (mainly Vernonia chamaedrys and Eupatorium polystachyum), 41.9 ± 0.8 cm (range 27–60 cm, n  =  38) above the ground. Clutch size is two (91%) or three eggs (n  =  43), which measure 16.22 ± 0.51 mm by 11.93 ± 0.28 mm (n  =  10), and incubation, which is performed by the female, lasts 12 days. Average nest attentiveness during incubation was 60 ± 5% (n  =  5) with 20–31 min on-bouts. Males help feed the nestlings beginning on the fifth day after hatching. Provisioning visits/hr averaged 4.6 ± 0.7 (n  =  6) and fema...